Stirling cycle engine with wave-cam means interconnecting pistons and drive shaft thereof



Oct. 1, 1968 D A. KELLY 3,403,508

STIRLING CYCLE ENGINE WI TH WAVE-CAM MEANS INTERCONNECTING PISTONS ANDDRIVE SHAFT THEREOF Filed Dec. 9, 1966 4 Sheets-Sheet 1 PM; EP4 5 I0 \f:n 6

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Oct. 1, 1968 D. A. KELLY 3,403,508

STIRLING CYCLE ENGINE WITH WAVE-CAM MEANS INTERCONNECTING PISTONS ANDDRIVE SHAFT THEREOF Filed Dec. 9, 1966 4 Sheets-Sheet 2 PHAJ 0046/94/ 1lama/7:

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INVENTOR.

Oct. 1, 1968 D. A. KELLY 3,403,508

STIRLING CYCLE ENGINE WITH WAVE-CAM MEANS INTERCONNECTING PISTONS ANDDRIVE SHAFT THEREOF Filed Dec. 9, 1966 4 Sheets-Sheet 3- Fig.5"

o. A. KELLY 3,403,508 STIRLING CYCLE ENGINE WITH WAVE-CAM MEANSINTERCONNECT ING Oct. 1, 1968 PISTONS AND DRIVE SHAFT THEREOF Filed Dec.9, 1966 4 Sheets-Sheet VPHMUCDM ENTROPY VOLUME IN VEN TOR.

'BYAMZ/O/Kg 6k- United States Patent 3,403,508 STIRLING CYCLE ENGINEWITH WAVE-CAM MEANS INTERCONNECTING PISTONS AND DRIVE SHAFT THEREOFDonald A. Kelly, 5806 69th Place, Maspeth, N.Y. 11378 Filed Dec. 9,1966, Ser. No. 600,478 7 Claims. (Cl. 6024) ABSTRACT OF THE DISCLOSURE AStirling cycle engine having a drive shaft and a plurality of pairs ofpower and displacer pistons arranged radially about said drive shaft,and a wave-cam coaxially mounted upon the drive shaft for rotationtherewith, said wave-cam having a cam track slidably associated withsaid pistons, whereby the reciprocating movement of the pistons impartsrotational movement to the drive shaft.

Various types of Stirling cycle engines are known, such as theconventional dual-coaxial reciprocating engine now in use, side-by-sidepiston types and L types. The currently used dual-coaxial piston engineis pressurized and operates at good efficiencies but due to itsconfiguration is hampered by an excessive number of rods and linkages.This complex linkage system is a drawback to the simple ganging of thecylinder banks to achieve efficient, high power-to-volume Stirlingengines.

The present novel design attempts to circumvent some of thesedeficiencies of the current engine by the application of a wave-cam onthe drive shaft. This cam drive arrangement allows the classic dualside-by-side Stirling cylinders to be efficiently housed within aminimum volume unit. This cam drive advance permits utilization of aminimum number of working parts inasmuch as the pistons are directlyconnected to the cam track to thereby eliminate connecting rods, linksand pins and the consequent wear of these parts. The present cam is oftwin wave configuration thereby providing for a complete excursion ofeach piston within a 180 degree, /2 revolution of the drive shaft. Inthis arrangement, the required half-stroke phasing between the pairs ofStirling pistons is provided by placing the piston pairs at 45 degreeson the cam track. Since the twin wave-cam has been determined highlyeffective in View of its optimum displacement angle, the complete numberof cylinders comprises four pairs or eight.

The aforementioned cylinders are considered in pairs since the displacercylinder is the gas pressure generator for the power cylinder, whichmeans that for the twowave-cam there are four effective power cylinders.

The number of power cylinders may be increased by adding another cam intandem with its cylinder bank, such arrangement being advantageous tothe end of minimizing shaft and bearing problems. The two cams shouldpreferably be 22 degrees out of phase to provide a maximum number ofpower pulses for smooth rotation with a minimum of vibration.

It will, therefore, be understood that the functions of the side-by-sideStirling pistons prevail in the present cam arrangement, with thenecessary phasing between pistons being provided by their relativeposition on the cam track of the instant wave-cam.

Since the stroke of the multiple pairs of pistons are the same in viewof the fixed cam throws, the bore of the displacer piston may be variedto obtain the optimum volumetric ratio.

The classic Stirling closed cycle is basically an externally heatedengine in which a constant volume of gas lot:

is alternately heated and cooled to produce the half-power stroke andhalf-pull stroke on the power piston.

More specifically, the conventional Stirling engine consists of dualcoaxial pistons, one displacer and one power piston reciprocating withina common cylinder. The approximately degree phase angle at thecrank-disc keys the cycle so that the displacer piston follows the powerpiston downward for the half-power stroke, thereby allowing theexpanding gases to push effectively on the power piston. The two pistonsare in-line and connected in phase to a common crank-disc and shaft. Inthe present arrangement, the displacer piston follows the power pistonon the upward half-pull stroke.

Accordingly, and in consonance with the foregoing, it is a generalobject of the present invention to provide a simplified Stirling cycleengine while retaining all the characteristic efficiency of the cycle.

Another object of the invention resides in the achievement of amultiple-piston Stirling engine in the form of a minimum volume module.

A further object of the invention is to provide a relatively simpleStirling cycle engine which efficiently conducts heat to the displacerbore and maintains low ambient temperatures at the cold volume thereof.

Another object of the invention is to achieve maximum operatingefficiency in a Stirling engine through the adoption of new and improvedthermal saturation means.

A further object of the present invention resides in the provision of adevice of the foregoing character which will operate without fluidlubrication and at a minimum friction level.

Another general object of the instant invention is to provide a deviceof the described character which will be simple in structure, economicalof manufacture, and highly effective in use. Other objects andadvantages of the instant multipiston cam Stirling engine will be setforth in part hereinafter and in part will be obvious herefrom, or maybe learned by practice of the invention, the same being realized andattained by means of the structure defined and pointed out in theappended claims.

The accompanying drawings referred to herein and constituting a parthereof, illustrate the invention, and together with the description,serve to explain the principles of the invention.

FIGURE 1 is a front elevational cross-sectional view of the engine;

FIGURE 2 is a side elevational partial cross-sectional view of theengine;

FIGURE 3 is a diametrical partial cross-sectional view of the engine;

FIGURE 4 is a phasing diagram of the relative positions of the displacerand power pistons and the location of the heating and cooling sourcesrelative to said pistons;

FIGURE 5 is an exploded perspective View illustrating the various partsof the engine;

FIGURE 6 is a perspective view of the piston housing;

FIGURE 7 is a graphic representation of the pressurevolume andtemperature-entropy characteristics of the engine.

The present preferred embodiment of the invention as illustrated in theaccompanying drawings will now be described, twin wave-cam 1, anessential element thereof being clearly seen in FIGURE 5. As showntherein, said wave-cam comprises identical wave portions A and B and isattached to drive shaft 2 to thereby transform the reciprocating thrustsof the power pistons 3 into rotary motion, the latter of which isimparted to said drive shaft.

Said power pistons, generally designated herein by numeral 3 andindividually as P1, P2, P3, and P4, slide within power bores 4 andthereby transmit motionto cam track 5 of wave-cam 1 through rollerbearings 6, pins 7 being provided to secure said bearings to the sidesof the power pistons, respectively, as shown. Piston rings 38 are fittedinto grooves 39 in the pistons 3.

The drive shaft 2 revolves on and is supported by thrust roller bearings8 which are mounted in piston housing halves 9 and 10, said housinghalves being substantially identical, such halved arrangement permittingexpedient assembly and disassembly of the engine. Said housing halvesare mutually secured by tensile bolts 11 and nuts 12, gasket 13 beingprovided therebetween for sealing purposes.

The displacer pistons, generally designated by numeral 14 andindividually as D1, D2, D3, and D4, are reciprocated by the cam track 5through roller bearings 15, pins 16 being provided to secure saidbearings to yolk members 17, said displacer pistons being slidablyreceived within displacer bores 18 as shown.

Sealing plate 19, attached to the displacer pistons, provides a sealbetween said plate and displacer slot 20, the latter being integrallyprovided in said piston housing as shown. Since the expanding workinggas, e.g., air, must not escape into the cam volume region 20', the sealplates are required to effectively seal each displacer slot 20 withminimum sliding friction.

Said displacer pistons are preferably fitted with ball bearings 21 whichare rotatably journalledl by pins 22 within recesses provided within thelongitudinal sides of said pistons to thereby reduce piston side playand friction within the displacer cylinder, said displacer pistonshaving sutficient wall gap with respect to said bores 18 to therebyallow the working gas to be shuttled back and forth within the displacerbores.

End flanges 23 position and support pressure seals 24 at each end of thehousing and are secured to each housing half by screws 25. Liquidsealant is preferably used to seal the joint between the end flanges andthe housing halves.

Heat cylinders 26, formed of copper or other suitable heat conductivematerial, conduct heat from an external heat source, e.g., a flame jetor other suitable heat source, to one end of each displacer bore 18,said heat cylinders being insulated from the housing halves by dint ofinsulation liners 27, said liners further providing a pressuretight sealand allowing for the expansion of the heat cylinders. Cooling cylinders25', also formed of copper or other suitable heat exchange material,extend as shown, contiguously with respect to cooling bore volumes 28'to thereby cool said volumes by simple heat exchanges between said boresand the cooler temperature ambient said piston housing.

Two thrust collars 28 are secured to the drive shaft 2 at each endthereof and cont-act the inner race of the thrust roller bearings 8 totransmit thrust and to remove end play in the drive shaft.

Regenerator bores 29 and regenerator filaments 30 are locatedapproximately midway in transfer ducts or conduits 31, said ducts beingprovided to connect each displacer bore 18 with an adjacent power bore4, such connections being indicated in FIGURE 4 of the drawings. It isnecessary to connect the midpoints of the displacer bores with the topsides of the power bores 4 so that a proper thermal balance ismaintained within the displacer bore 18.

As shown, ducts 31 are all sloped in the same direction in accordancewith piston phasing requirements. The said regenerator filaments 30,located within the regenerator bores 29 within the transfer ducts 31,provide the means for storing the transmitted heat during one half-cycleand giving it up on the reverse flow for preheating of gas for the nextheating half-cycle.

With reference now to FIGURE 3, fine saturation filaments 32, as shown,are uniformly dispersed within the hot and cold ends of displacer bores18, said filaments being formed of beryllium-copper or other suitableheat conductive material. Those filaments disposed adjacently of saidheat and cooling cylinders, are, as shown, connected thereto at 26, saidfilaments being effective in uniformly heating and cooling bore volumes27' and 28', respectively, and being adapted to fiex on contact with thereciprocating displacer pistons.

Inasmuch as each pair of adjacent bores containing respective pairs ofpower and displacer pistons P1, D1; P2, D2; and P3, D3; and P4, D4 coactindependently of the other pairs of adjacent bores, each of said pairsof bores is preferably fitted with gas filler valves 33, a pressuregauge 34, a safety plug 35 and a temperature gauge 36, as shown, therebyallowing the user to regulate and observe the operating characteristicsof each pair of respective bores. Two filler valves 33 are provided, oneat each end of the power bores 4, since the power piston seals offvolumes 36 and 37' located, respectively, at opposite ends of saidbores. In operation, the under ring volumes act as the bounce chamberduring the cooled gas contraction and provide the thrust for anapproximate half-stroke.

The pressure gauges 34 are preferably located at the power bore sincesuch location will be at substantially mean temperature and workingpressure, although subject to the high and low cycling surges. Thetemperature gauges 36, as shown, are preferably arranged in proximitywith respect to heat cylinders 26, to thereby monitor heat fiowing toeach bore.

As a summary, then, the operation of the present invention is asfollows: Each cylinder consists of two bores, placed side by side, withan interconnecting channel between them, and with a power piston in onebore and a displacer piston in the other (see FIG. 1). In order totransfer motion from the pistons to a rotatable shaft :1 wave cam isutilized, with the pistons riding on the cam face, and the variousbores, and therefore the pistons themselves, being equa'lly spacedaround the periphery of the cam. The displacer piston is a loose fitwithin its bore to let air flow around it. The power piston is a tightfit within its bore and is timed to move slightly behind the displacerpiston. As the power piston is pushed in (on starting or by flywheelmomentum), it forces air through the channel connecting the bores, andcompresses this air in the cold end of the displacer bore.

When the power piston is at the top of its stroke, the displacer pistonhas moved halfway down its bore and has transferred some of the cold airaround its loose fit, up to the hot end of the bore. The compressed airexpands as it is heated and drives the power piston out, while stillmore air is transferred as the displacer moves further down.

As the displacer moves up again it transfers air back to the cool spaceto be recompressed. Because of slight air loss, the cooled air is belowatmospheric pressure, which therefore tends to suck the power piston infor another power stroke.

Although the preferred embodiment of the Stirling cycle engine structurehas been described, it will be understood that within the purview ofthis invention various changes may be made in the forms, details,proportion and arrangement of parts, the combination thereof and mode ofoperation, which generally stated consists in a device capable ofcarrying out the objects set forth, as disclosed and defined in theappended claims.

What is claimed is:

1. In a reciprocating Stirling cycle engine which has no valves or sparkplugs and which operates on the heating and cooling of the same air andhaving multiple pistons and a pressurized gaseous medium, thecombination comprising a piston housing, a drive shaft rotatably mountedwithin said housing, wave-cam means mounted on said drive shaft forrotation therewith, a plurality of elongate bores within said housing,said bores each having a longitudinal axis and a forward and a rearwardend and being radially arranged with respect to said wavecam means, saidlongitudinal axes and said drive shaft being arranged in parallelism,multiple groups of coacting pairs of power and displacer pistons, rollerbearings integral with each power and displacer piston for rollingcontact with the wave cam, each of said pairs of pistons being slidablyreceived within respective pairs of adjacently disposed bores foralternating phase reciprocation therewithin, passage means disposedbetween opposite ends of said displacer pistons and communicating withthe top of said pistons.

2. The combination set forth in claim 1 including bear ing meansinterposed between one of the pistons of said coacting pairs of pistonsand the bore in which said piston is received.

3. The combination set forth in claim 2 wherein said one of the pistonsis provided with a! flat sealing plate connected to one side thereof andbeing received within a groove in the housing to prevent loss of thepressurized gaseous medium, and yoke means secured to said sealing platefor supporting the roller bearings.

4. The combination set forth in claim 1 including a relatively thin,flexible thermal conductive filament disposed at at least one end ofsaid displa'cer piston bores.

5. The combination set forth in claim 1 including thermal regenerationmeans disposed within the said passage means of the piston housing.

6. The combination set forth in claim 1 including heat conducting meansarranged proximately with respect to an end of each of said displacerbores, and a thermal saturation filament interposed between each of saidheat conducting means and a relative displacer piston.

7. The combination set forth in claim 1 wherein said wave-cam means isof circular configuration and includes a cam track disposed peripherallythereof, said cam track including a pair of identical wave portions,said wave portions being 180 degrees apart.

References Cited UNITED STATES PATENTS 1,006,269 10/ 1911 Philfer.1,229,009 6/1917 Allison. 1,828,353 10/1931 Bleser 12358 X 2,272,925 2/1942 Smith. 2,482,831 9/ 1949 Arden 123-145 2,712,483 7/1955 Ciaccia92--178 CARROLL B. DORITY, JR., Primary Examiner.

